Physical Origin of the Mechanochemical Coupling at Interfaces

TL;DR

This study uses DFT calculations to dissect the physical origins of mechanochemical responses at interfaces, revealing significant contributions from both interfacial bonds and the bulk material, influenced by stiffness and geometry.

Contribution

It provides a detailed analysis of the physical mechanisms behind mechanochemical coupling at interfaces, emphasizing the role of bulk deformation often overlooked.

Findings

Bulk elastic deformation significantly influences activation volume.

The mechanochemical response depends on interface and bulk contributions.

Activation volumes are finite and vary with contact geometry.

Abstract

We used density functional theory (DFT) calculations to investigate the physical origin of the mechano-chemical response of materials interfaces. Our results show that the mechano-chemical response can be decomposed into the contribution from the interface itself (deformation of interfacial bonds) and a contribution from the underlying solid. The relative contributions depend on the stiffness of these regions and the contact geometry, which affects the stress distribution within the bulk region. We demonstrate that, contrary to what is commonly assumed, the contribution to the activation volume from the elastic deformation of the surrounding bulk is significant and, in some case, may be dominant. We also show that the activation volume and the mechanochemical response of interfaces should be finite due to the effects on the stiffness and stress distribution within the near-surface bulk region. Our results indicate that the large range of activation volumes measured in the previous experiments even for the same material system might originate from the different degrees of contributions probed from the bulk vs. interface.